[miaculpa20]

Hi there, can anyone pls explain to me the matter of "claim". I have never heard of this untill I started to play online. Is it an American thing? M123

[barmar]

Claiming has been a part of bridge, both rubber and duplicate, since the beginning. It was presumably used in whist before that -- you can claim in practically any trick-taking game. There's an entire section in the Laws devoted to it (BBO's claim procedure is closer to the rubber bridge style than duplicate -- it doesn't have different rules depending on whether there's a director available to adjudicate claims that are refuted).

See Laws 68-71 for the official Laws regarding claims in duplicate bridge. But basically, once you're sure how many more tricks your side can take, you can claim those tricks to avoid wasting time playing it out. If you think the claimer made a mistake, you can contest the claim.